The invention relates to ink jet printers and to improved methods for making printheads for ink jet printers.
Ink jet printers continue to evolve to provide print engines having increased resolution at higher page throughput. However, higher throughput often means the printheads must operate with higher ejection frequencies which often increase the printhead temperature. Higher printhead operating temperatures and more chemically aggressive inks require more robust construction or modification in fabrication techniques to enhance the ability of the components of the printhead to withstand more extreme operating conditions and inks. For example, increased operating temperatures may cause failure of adhesives used to attached printhead components to one another. Failure of adhesion between protective layers attached to the semiconductor surface may invite corrosion from ink contact with unprotected surfaces including the electrical devices on the semiconductor surface.
What is needed therefore is an improved method for fabricating ink jet printheads to reduce the potential for corrosion from ink over the life of the printhead.
With regard to improving manufacturing techniques so as to provide printheads having increase reliability over the life thereof, a method for improving adhesion between a polymeric planarizing film and a semiconductor chip surface is provided. The method includes depositing resistive, conductive and/or insulative materials to a silicon wafer surface to provide semiconductor chips for ink jet printers. The wafer surface is treated with a dry etch process under an oxygen atmosphere for a period of time and under conditions sufficient to activate the surface of the wafer. A polymeric planarizing film is applied to the activated surface of the wafer. As a result of the dry etch process, adhesion between the planarizing film and the wafer surface is increased over adhesion between a planarizing film and a wafer surface in the absence of the dry etch treatment of the wafer surface.
In another aspect, the invention provides a semiconductor chip for an ink jet printhead. The chip includes silicon having a device surface and one or more metal or metal oxide layers providing active devices on the device surface. The device surface is activated for bonding a planarizing film thereto. A planarizing film is attached to and covers at least a portion of the activated surface of the semiconductor chip. The surface is activated by treating the surface with a dry etch process under oxygen atmosphere to provide increased adhesion between the planarizing film and the device surface.
An important advantage of the invention is that the printhead exhibits improved life even when operating at higher temperatures and when using more chemically aggressive inks. A factor in the improved life of the printhead is the decreased tendency for the planarizing film to delaminate from the device surface of the chip when a printhead is made by the process of the invention. Because the planarizing film of the invention is more prone to remain completely attached to the device surface, corrosion of the device surface by ink contact therewith is significantly reduced. In comparison, printheads made by planarizing unactivated device surfaces are more prone to delamination between the planarizing film and chip surface than printheads made according to the invention. Delamination of the planarizing film provides an avenue for ink corrosion of the device surface of the chip.